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Improving wireless Networks

Passive Intermodulation

Improving Wireless Networks

© Kaelus 2012. All rights reserved.

CONFIDENTIAL AND PROPRITARY INFORMATION OF KAELUS

What is Passive Intermodulation (PIM)?What is Passive Intermodulation (PIM)?What is Passive Intermodulation (PIM)?What is Passive Intermodulation (PIM)?


What is Passive Intermodulation (PIM) ?

PIM = Noise generated by the interaction between the multiple Tx signals and passive

non-linear junctions in the RF path.

Increasing the received Noise floor thus reducing base station sites coverage and

capacity.

f1 f2

f1+f2f2-f1

2f1-f2

2f1 2f2

2f2-f13f2-2f1

4f2-3f1

3f1-2f24f1-3f2

InterferenceInterference

Desired

PIM generated products will affect received band (UL) by



For wireless operators

f1 f2

f2-f1

2f1 –f23f1-2f2

4f1-3f2

Interference

GSM, UMTS, LTE, CDMA, WCDMA

DL - DownlinkUL - Uplink

TX frequencies



f1 f2

f2-f1

2f1 –f23f1-2f2

4f1-3f2

Interference

PIM depends on:

•Number of possible frequency combinations (more frequencies more possible

combinations)

•The frequencies TX power ( + 1dBm Tx Power = + 2.5 to 3 dBm on PIM)


TX frequencies


PIM is getting more complex with

f1 f2

2f1 –f23f1-2f2

4f1-3f2

RX operator 1

By changing the TX frequencies the IM products change


TX operator 1

f1 f2

2f1 –f23f1-2f2

4f1-3f2

RX operator 1


TX operator 1

GSM900 Example



But now you have GSM900 with UMTS900 or LTE1800

f1 f2

2f1 –f23f1-2f2

4f1-3f2

RX operator 1


TX operator 1

Not a lot of space to change TX frequencies, a UMTS carrier that normally is 5 MHz or

LTE 10 MHz carrier and more combination possibilities

UMTS

Or

LTE

Carrier



Networks evolution towards:

• Indoor or outdoor complex DAS

systems (shared by several operators)

• Site sharing with multiple transmit

carriers (same RF infrastructure for

multiple operators)

• Multi-technology sites (GSM 900 MHz,

GSM 1800 MHz, UMTS 2100, UMTS 900

MHz, CDMA 450, LTE800, LTE2600…)

Combining UnitGSM 900GSM 1800WCDMA

OP

1B

TS

OP

2B

TS

OP

3B

TS

OP

1B

TS

OP

2B

TS

OP

3B

TS

OP

1N

od

e B

OP

2N

od

e B

OP

3N

od

e B

Lo

ad

1800/W

CD

MA

900/18

00

Triplexer

RF Output ports

PSPS

PSPS

PSPS

PSPSOutdoor

area

AntAnt

AntAnt

AntAnt

PSPS

AntAnt

AntAnt

Ant

PSPS

PSPS

AntAnt

PSPS

AntAnt

AntAnt

AntAnt

PSPSAntAnt

PSPSAntAnt

PSPSAntAnt

PSPS

AntAnt

IndoorArea 1

IndoorArea 2

IndoorArea 3

IndoorArea 4

IndoorArea 5


How it appears on the Radio Access Network


PIM SourcesNon-linear metal-to-metal contacts:

• Loose RF connectors.

• Poorly prepared RF cable terminations

• Improperly mated / misaligned parts

• Cracked / cold solder joints

• Loose mechanical fasteners (screws, rivets)

Traditional sweep (RL or DTF) testing many times does not identify these

problems.


� First edition of IEC 62037 was published on 9/16/1999. (>14 years ago!)

� Purpose:

� To establish a standard test method for measuring Passive

Intermodulation (PIM)

� Provide a method to compare the PIM performance of different devices

� Key recommendations of the specification:

� Third Order IM products typically represent the worst case condition of

unwanted signals; therefore measuring IM3 characterizes the DUT

� PIM comparisons should be done at the same power level.

� 2x 20 W recommended for mobile communications systems.

� Devices should be subjected to an “impact” or “movement” while PIM

testing

PIM test specification IEC 62037


PIM Test equipment transmits 2 frequencies at high power into the system under test and

measures the magnitude of the interference generated at the known IM3 frequency.

The fault location is found by “tapping” on interconnections and components (dynamic

test) during the test looking for spikes in PIM magnitude.

PIM Source

PIM

TX 1TX 2

TX 1

TX 1

TX 2

TX 2

PIM Test Equipment

PIM

How to test PIM?


� IEC 62037 requires that devices be subjected

to an “impact” or “movement” while PIM

testing. Referred as “Dynamic” testing

� Loose mechanical contacts in the field may

not generate PIM until subjected to a future

environmental stress (thermal cycling, ice

loading, wind loading, etc.)

� PIM level must stay below the specified

maximum at all times during a dynamic test

FAIL

No tapping Tapping

PASS

Poor RF Connection

PIM tests must be dynamic


Repairing IM3 reduces ALL IM products.

Metal flake

11th Order

-93 dBm

9th Order7th Order

5th Order3rd Order

-60 dBm

Outside PCS

Rx band for

F1 & F2

selected

Spectrum Analyzer Mode

PIM Severity


Possible to have Same Band intermodulation issues

3rd order

5th order

7th order

• GSM900

935 MHz 960 MHz890 MHz 915 MHz

900 GSM Rx band 900 GSM Tx Band

•

935 MHz 960 MHz890 MHz 915 MHz

900 GSM Rx band 900 GSM Tx Band

• GSM1800

1805MHz 1880MHz1710MHz 1785MHz

1800GSM Rx band 1800GSM Tx Band

•


1800GSM Rx band 1800GSM Tx Band

• UMTS2100


2100 UMTS Rx band 2100 UMTS Tx Band

•


2100 UMTS Rx band 2100 UMTS Tx Band


Also, Cross Band intermodulation issues involving UMTS

• DCS1800 into UMTS2100

1805MHz 1880MHz 1920MHz 1980MHz

1800GSM Tx band UMTS2100 Rx Band

3rd order

5th order

And with LTE there are multiple combinations nowadays


� Main search focus on:

� General – CDR, CSR, CSSR

GSM

� GSM Mean interference on Idle (IOI)

� TCH Completion Rate and Drop %

� TRAFFIC RATE Erlangs

� TCH Assignment Rate

� SDCCH Assignment rate and drops

� HO Success Rate

� UL Quality

� Erlang Minutes Per Drop

� DROP_AFTER_TCH_ASSIGN

� SDCCH_RADIO_FAIL

� CDR data and voice

� RRC Success rate%

� RAB Establishment Success %

� Voice Traffic Erl

� PS Traffic (Mb)

� Average Throughput

� RTWP

� RSSI

UMTS

Where to look for PIM on statistics?


KAELUS field trial evaluationKAELUS field trial evaluationKAELUS field trial evaluationKAELUS field trial evaluation


KAELUS trials:

• >430 feeder lines surveyed.

• 26 Operators and OEMs, 17 countries

• Many PIM problems recorded

• Few VSWR problems found

The sites were originally commissioned

with Sweep test equipment so it is no

surprise that the VSWR results are good

PIM Survey in EMEA by KAELUS

Comment on Statistics

On the trials our customers select general bad

performance sites to perform the PIM tests.


• The PIM defects found were

primarily due to workmanship

issues at the RF connections.

• Many lines had multiple defects

• KPI improvements reported on

the majority of sites that PIM was

detected and repaired at site

PIM Survey in EMEA by KAELUS


Poor cable

preparation

Dirt / trash


Poor cable

preparation

CONFIDENTIAL AND PROPRITARY INFORMATION OF KAELUS 23232323

Antennas closely pointing

to metallic structures with

oxidation or loose screws


KAELUS Case StudiesKAELUS Case StudiesKAELUS Case StudiesKAELUS Case Studies


GSM 900 + GSM 1800 + UMTS 2100 Multi-operator

DAS system


GSM 900 + GSM 1800 + UMTS 2100 Multi-operator DAS system

Tapper

1

Triplexer

2 3 4

DCS

UMTS

MultibandCombiner

6

Op2

Op3

Tapper

Splitter

Antenna

Antenna

Splitter

Antenna

Antenna

8 95

7

GSM 900BTSOp1


Tapper

1

Triplexer

2 3 4

DCS

UMTS

MultibandCombiner

6

Op2

O03

Tapper

Splitter

Antenna

Antenna

Splitter

Antenna

Antenna

8 95

PIM = - 60 dBm

PIM = - 90 dBm

After, connector cleaning,

replacement and Jumper interventions

7



PIM detection and

correction date


28282828

Connector problem

(node 8)


UMTS2100 Rooftop Site


3G Rooftop

Urban dense site

Surge Arrestors were the source of PIM

After their replacement


After PIM changes


KAELUS PPIM SolutionsKAELUS PPIM SolutionsKAELUS PPIM SolutionsKAELUS PPIM Solutions


� Summitek Instruments has been producing “bench

top” PIM test systems for more than a decade

� Summitek has delivered more than 800 BPIM

systems worldwide

� These systems have been used by RF equipment

manufacturers to reduce PIM in their component

designs

PIM testing is not new!


What is relatively new is Portable PIM test equipment.

� “Portable” PIM test equipment enables system level

testing to be conducted at the cell site.

� Kaleus has delivered more than 6000 systems

worldwide.

� On site PIM testing reveals:

� Installation workmanship issues

� Component damaged during installation

� Component damaged in transit


• High Power – Premium

• Adjustable power (2 – 20W)

• Adjustable frequencies

• Rugged construction

• Integrated transit case

• Panel PC with touch screen interface,

on-board reporting

PIM Test Equipment: iQA Series


• Adjustable power (+0.1 to 20W)

• Highly portable and ruggedized design – ideal for top-of-tower

testing

• Includes tablet for safe, hands-free dynamic testing at the top of a

tower

• Battery powered

• On board, touch screen interface available for local control

• Includes the Kaelus industry leading report generator

PIM Test Equipment: iPA Series

CONFIDENTIAL AND PROPRITARY INFORMATION OF KAELUS-37-

© 2012 Kaelus Inc. All Rights Reserved

www.kaelus.com

Contact Us:

Americas

+1.303.768.8080

Asia Pacific, Africa

+61.(0).7.3907.1200

China

+86.21.6084.2200

Europe, Middle East, India

+44.(0).1383.437920

Follow @KaelusRF:

Thank you!

The NetherlandsLivingston TEMS

Nijverheidslaan 41

3903 AN Veenendaal

+31 318 588 688

BelgiumLivingston TEMS

Grote Steenweg 48

B-2550 Kontich

+32 15 286 281

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